Tobacco smoke filtering device

ABSTRACT

This disclosure relates to a tobacco smoke filter which removes tars through condensation and precipitation. An inlet nozzle protrudes into a smoke expansion chamber of predetermined size. Smoke exits from the nozzle at high velocity and disperses and expands in the chamber with a resultant turbulence and temperature drop. Water vapor precipitates on the chamber surfaces and tars coalesce thereon. The filter is constructed and arranged to prevent blockage by coalesced tars and to operate within a predetermined range of pressure loss while efficiently removing tars from the tobacco smoke.

United States Patent William F Van Eck 228 Main St., East Haven, 06512;Warren R. Jewett, Orange, both 01, Conn. [21] Applr No 803,712

I 22] Filed Mar. 3, 1969 [45] Patented Aug. 24, 1971 [73] Assignee SaidVan Eek, by said Jewett [72] Inventors [54] TOBACCO SMOKE FILTERINGDEVICE 27Claims,24DrawingFigs.

[52] U.S.C1 131/2618, 13l/2]0,l3l/212A,l31/212R,l31/2l3 [51] 1nt.CLAZ4d1/UQ, A24f 7/04, A24 f 13/06 [50] FieldofSearch 131/105,211,212,212A,213,218,261B

[56] References Cited UNITED STATES PATENTS 46,505 2/1865 Smith&Brown...l31/212(A) 3,269,394 8/1966 Curtis,Jr. l31/10.5UX

3,318,312 5/1967 CurtisJr, 131/105 3,433,231 3/1969 Siragusa 131/105FOREIGN PATENTS 714,659 12/1941 Germany l3l/212(A) 13,535 1390GreatBritain..... 131/212(A) 559,115 3/1957 Italy 131/105 PrimaryExaminer-Samuel Koren Assistant Examiner-J. F. Pitrelli Artorney-De1ioand Montgomery ABSTRACT: This disclosure relates to a tobacco smokefilter which removes tars through condensation and precipitation. Aninlet nozzle protrudes into a smoke expansion chamber of predeterminedsize. Smoke exits from the nozzle at high velocity and disperses andexpands in the chamber with a resultant turbulence and temperature drop.Water vapor precipitates on the chamber surfaces and tars coalescethereon. The filter is constructed and arranged to prevent blockage bycoalesced tars and to operate within a predeten mined range of pressureloss while efficiently removing tars from the tobacco smoke.

PATENTED M82419?! SHEET 1 OF 3 INVENTORS Wflham F. Van Ea) \JOoxran R.SewesPr BY r D90% 0m W\ TOBACCO SMOKE FILTERING DEVICE This inventionrelates to the removal of tars and other particulate substances fromtobacco smoke, and more particularly relates to new and improved devicesfor precipitating tars from tobacco smoke.

At the present time, by far the great majority of tar filteringarrangements use cellulose-filaments in various amounts, with variousbinders and additives. The purpose of such filters either in cartridgeform or as filter tips on cigarettes is to trap or collect the tar byvirtue of the maze formed by the filaments. The path the smoke travelsin passing along the length of the filter tip may be up to approximatelynine-sixteenths of an inch.

Such filters attempt to precipitate the tar by providing a large numberof contacting surfaces. However, such filament type filters provide alarge through air passage as may be exemplified by rolling the filterand finding it will decrease from approximately a five-sixteenths inchdiameter filter tip into a one-eighth inch diameter bundle or rod. Itmay readily be appreciated that to make the filament type filter moreeffective, the bundle of filaments would have to be packed tighter. Thisdecreases the effective air passage and increases the resistance, whichis highly objectionable to the smoker.

Another type of filter which appears to be more effective than thecommon fiber filter is one in which the smoke drawn from a cigarette ispassed through a small orifice to substantially increase the velocityand direct it onto an impingement wall or baffle placed a very smalldistance behind such orifice, perhaps 0.030 inch. In such structure, thesmoke from the cigarette may pass through the orifice at a speed inexcess of 100 feet per second. When the smoke impinges on this wall, theheavier particles therein will tend to collect on the wall and furtherwill be released from the gas stream as the gas stream changes directionto go around the wall. This type of filter may be considered a fairlyeffective arrangement for removing the heavier tars from tobacco smoke.However, it adds a static pressure loss which may be uncomfortable orunacceptable to the smoker. This may easily be appreciated when it isconsidered that the impingement barrier is substantially in contact withthe orifice and just enough clearance is allowed to attempt to preventthe tar formed by impingement from blocking further flow of gas.Measurements on one such device as shown in US. Pat. No. 2,954,779 haveshown the static pressure loss to be normally on the order of 28-40 mm.Hg. This pressure loss may increase where several cigarettes are smokedwith some time intervals in between. During the intervening time, thedeposited tars will tend to thicken and partially block the narrow gap.This results in increased resistance to air flow.

Other techniques include cooling the smoke through conduction whileusing metal parts. This type of filter construction has been usedpredominantly in pipe stems and has further included the use of a spiralpath. However, if the smoke is cooled too great an extent, the smokerfinds this objectionable.

Another way of removing entrained particles from tobacco smoke would bethrough expansion cooling and allowing the heavier particles toprecipitate from the gas. These devices, so far as is known, haveheretofore been rather elongated and required considerable length, andtherefore have not been acceptable. Additionally, such devices as havebeen known have not been efficient in the removal of tars.

So-called tars from tobacco smoke exist in gas form or micro droplets.Tobacco smoke, because of its composition of micro droplets of tar,water and other particles in suspension may be considered an aerosol.Tar precipitation from smoke is a complex, multifactored process. One ofthe factors involved is turbulence which is produced by resistance toair flow. Other considerations are surface characteristics; suddenchanges in the volume or direction of gas flow; condensation of watervapor produced by turbulence and a cooling effect as,

for example, through expansion of the smoke. The transport of tar andsmoke is, in effect, similar to a steam distillation phenomenon, andcondensation of water reduces the kinetic energy of the tar particlessufficiently to coalesce. This requires that a solid surface be presentin order for the tar to adhere thereto. Otherwise, the tar will remainin the gaseous vehicle and will be aspirated by the smoker.

The present invention provides tobacco smoke filters which generallyoperate on the principle of precipitation of tars. Due to the productsof combustion when smoking a cigarette or other tobacco, water isgenerated; If the cigarette smoke containing such water vapor isexpanded or decompressed under suitable conditions, a drop in thetemperature of the gas results which can lead to condensation of watervapor therein. This reduces the kinetic energy of the gas system andmicro tar droplet or particles coalesce upon contact with a solid orliquid surface. This provides liquid surfaces upon which the particlesmay further coalesce. Tar precipitators or filters embodying the presentinvention generally operate on the principle of the decompression orexpansion of the gas to release entrained or suspended particles.

It has been determined that in a tar precipitator or filter it is quiteimportant that the resistance introduced by such filter be held to aminimum. If the resistance to puffing becomes too great, the filter willbe discarded. I find that the precipitation qualities of the filter aregreatly improved by introducing turbulence into the gas flow. However,such turbulence must be so introduced that it does not increase theresistance to an unacceptable value.

It has also been determined that the relative volume of the expansionchamber to the smoke introduced therein is determinative of the amountof tar that may be precipitated. This, in turn, has a relation to theamount of surface area defining the chamber. If the chamber is toosmall, an undesired static pressure loss is presented. If the chamber istoo large, the particles remain in suspension and do not precipitate.There must be some pressure loss across the filter device.

In the present invention, moderate turbulence is introduced in acondensation or expansion chamber by increasing the velocity of thesmoke through a nozzle into the chamber to effect rapid deceleration ofthe smoke and resultant increase in volume against a pressure within thecondensing chamber. This produces a drop in the temperature of theexpanded smoke and resulting condensation of water vapor on the wallsdefining the chamber.

The present invention further preferably utilizes a nozzle whichprotrudes into the condensation chamber to prevent coalesced tars fromcollecting on the tip of the inlet opening or from flowing along thewalls of the chamber to the inlet opening and effecting a partialstoppage or blocking thereof which would lead to a greater pressure dropto the system. The present invention further utilizes tobacco smokeinlet nozzles of preferred shape and longitudinal contour to acceleratethe gas towards the condensation chamber without introducing anyobjectionable pressure drops across the nozzle.

An object of this invention is to provide new and improved devices forprecipitating tars and other particulate matter from tobacco smoke.

Another object of this invention is to provide new and improved devicesof the type described which offer no objectionable static pressure loss.

Another object of this invention is to provide devices of the typedescribed which include new and improved nozzle means for dispersingtobacco smoke to enhance decompression thereof and precipitation ofmatter therein.

Another object of this invention is to provide devices of the typedescribed having new and improved dimensional relationships to maximizeprecipitation of tars and other particulate matter.

A further object of this invention is to provide devices of the typedescribed wherein the surface area for precipitation of tars ad otherparticulate matter is enhanced.

A still further object of this invention is to provide new and improveddevices of the type described having new and improved means forproducing a slight degree of turbulence therein to enhance precipitationwithout producing an objectionable static pressure loss.

The features of the invention which are believed to be novel areparticularly set forth and distinctly claimed in the concluding portionof this specification. The invention, however, both as to itsorganization and operation, together with further objects and advantagesthereof may best be appreciated by reference to the following detaileddescription taken in conjunction with the drawings, wherein:

FIG. 1 is a longitudinal view in half section of a device embodying theinvention;

FIG. 2 is a view in perspective exploded showing one manner ofconstruction of the device of FIG. 1;

FIG. 3 is a view in longitudinal section of a modified embodiment of thedevice of FIG. 1;

FIG. 4 is a view partially in half section of a nozzle-defining devicewhich may be utilized with a filtering device embodying the invention;

FIG. 5 is a view in longitudinal half section of another deviceembodying the invention;

FIG. 6 is a view in longitudinal half section of still anotherembodiment of the invention and utilizing the nozzle-defining member ofFIG. 4;

' FIG. 7 is a view in longitudinal half section of another embodiment ofthe invention;

FIG. 8is a view of the device of FIG. 7 seen in the plane of lines 8-8ofFlG. 7;

FIG. 9 is a longitudinal half section of another device embodying theinvention;

FIG. 10 is a cross-sectional view seen in the plane of lines 10-10 ofFIG. 9',

FIG. 11 is another embodiment of the invention shown in longitudinalhalf section;

FIG. 12 is a view seen in the plane of lines 12-12 of FIG. 1 l;

FIG. 13 is a view in longitudinal half section of a multicavity deviceembodying the invention;

FIG. 14 is a sectional view seen in the plane of lines 14-14 of FIG. 13;

FIG. 15 is a longitudinal view of another device embodying theinvention;

FIG. 16 is a view seen in the plane of lines 16-16 of FIG. 15;

FIG. 17 is an enlarged sectional view of a nozzle defined in the deviceof FIGS. 15 and 16;

FIG. 18 is a view in longitudinal half section of a nozzle 'lefiningmember which may be utilized with various embodimen ts of the inventionshown;

F16 '9 is a longitudinal view partially cutaway and in section snowinganother nozzle defining member which may be utilized in variousembodimen s of the invention;

FIG. 20 is a longitudinal halt section view of a cartridge type deviceshown in a mouthpiece.

FIG. 21 is a longitudinal view of another cartridge type device within aholder;

FIG. 2 is a view seen in the plane of lines 22-22 of FIG. 21;

FIG. 23 is a longitudinal view of another cartridge device embodying theinvention; and

FIG. 24 is a view seen in the plane of lines 24-24 of FIG. 23.

In FIGS. 1 and 2 are shown a first tar precipitator embodying theinvention. This tar precipitator or filter 10 comprises a generalcylindrical housing 11 having oppositely disposed end walls 12 and 13which are shown as received within the conventional filter wrapper 14 ona cigarette 15.

As smoke is drawn from the cigarette 15, it enters the chamber 16through nozzle 17. Nozzle 17 is selected to protrude into chamber 16 forreasons hereinafter described. The smoke leaves chamber 16 throughopening 18 defined in end wall 13. The walls 18a defining opening 18also project into chamber 16. Nozzle 17 is provided with an exteriorextension 17b and spacer tabs 2110 are provided for spacing the filter asmall distance from the end of the cigarette.

As smoke is drawn through nozzle 17 it enters chamber 16, substantiallydecreases in velocity and is decompressed, or expands. Upon expansion,the smoke cools and the water vapor therein precipitates which collectsthe tars on the walls defining chamber 16. The degree of relativeexpansion would be greater with the nozzle 17 being made smaller.However, this would also increase the air flow resistance.

The average smoker aspirates about 35 ml. of air and smoke in one puff,which has a duration of close to 2 seconds. With this volume of smokeand air in approximately 2 seconds, the inlet port or opening 17 shouldhave a diameter of from approximately 0.025 inch to 0.033 inch. Theopening must not be so small that an undue resistance to air flow iscreated.

Excellent tar precipitation is obtained by a chamber volume of about anumerical factor of to 300 times the cross-sectional area of the inletopening where the units of measure are in millimeters.

In the filter shown in FIGS. 1 and 2, the outlet opening 18 should havean area which is substantially twice as great as the area of the inletopening. The inlet and outlet openings are offset with respect to eachother so that there will be no straight line or direct flow of smokefrom inlet to outlet openings.

The openings 17 and 18 are defined by nozzlelike projections 17a and 18ainto chamber 16. The condensation of water droplets and precipitation oftar could occur on the inside end walls 12 and 13 and, due to gravity orhandling of the cigarette, such precipitates could block or tend toblock the passages 17 and 18, which would result in increased resistanceto air flow and a higher static pressure drop. In order to prevent suchaction the projections 17a and 18a defining nozzles are provided. Theprojection 18a prevents the suctioning of any precipitated and coalescedtars into the outgoing air stream.

The actual cigarette is spaced from the filter by the tabs 20a whichcould also take the form of a complete cylindrical extension. Thepurpose of this spacing is to trap any tars precipitated by turbulenceat the end of the cigarette and prevent entrance into nozzle 17.

The device of FIGS. 1 and 2 is shown as a two-part structure comprisinga cylindrical containerlike member 19 which provides both sidewall 11and end wall 13 and a closure member 20 which provides end wall 12. Sucha filtering device may be made in this manner or may be made in twosemicylindrical pieces with the centerline of openings 17 and 18residing in the same plane but offset from each other.

An alternative embodiment of FIGS. 1 and 2 is shown in FIG. 3 andcomprises a cylindrical housing 21 having oppositely disposed end walls22 and 23 defining a chamber 24. The end walls 22 and 23 haveprojections 25 and 26, respectively, thereon. Such projections definenozzlelike inlet openings 27 and nozzlelike outlet openings 28. Theoverall dimensional relationship of the device of FIG. 3 with respect tothe chamber volume and the cross-sectional area of the inlet and outletopenings would be substantially the same. However, a compensating factorwould have to be introduced for the greater resistance through thesmaller openings.

To further guard against the accumulation of precipitated tars about theinlet nozzle, the end piece 20a may be formed with an opening adapted toreceive a nozzle defining member 20b, as shown in FIG. 4, defining aninlet opening and nozzle into the chamber 16. This provides traps 29 and30 which further aid in preventing the creep back of any precipitatedtars from blocking or restricting the inlet opening.

The introduction of turbulence into the system has been found tosubstantially aid in the precipitation of tars. A twopart filter element31, as shown in FIG. 5, of generally cylindrical shape, only one-half ofwhich is shown, comprises a cylindrical housing portion 32 havingoppositely disposed end walls 33 and 34 affixed to the end of acigarette 15, then covered with a filter wrapper paper 14. A projectionor box extending into the chamber 35 defines a nozzlelike inlet opening37. Extending from the sidewalls are baffles 36 which define anelongated path between inlet opening 37 and outlet opening 38 in endwall 34.

The baffles 36 are spaced from opening 37 and 38, respectively, asufficient distance such that there is no impingement effect, oressentially any resistance to gas flow. The purpose of the baffles 36 isto make the gas flow change direction to prevent any straight-througheffect, to provide surfaces for precipitation of water vapor and tars,and introduce some turbulence to aid in precipitation of tars.

The positioning or the shape of the baffling means, as exemplified bythe turbulence introducing means is not critical so long as it is spaceda sufficient distance from the inlet opening so that expansion of thegases occurs without high velocity impingement thereon.

In FIG. 6, a filter 40 comprising sidewalls 41 and end walls 42 and 43has arranged therein a baffielike member 44 which is angularly disposedwith respect to both the inlet and outlet opening and whose function isto make the gas change directions between the inlet and outlet openingswithout introducing any substantial static pressure loss. The filter 40of FIG. 6 is provided with the type of nozzle defining member b shown inFIG. 4, defining both the inlet and outlet openings. Again the inlet andoutlet openings reside in a common plane through the centerlines of theinlet and outlet openings so that the filter 40 may be made in twomating halves. Preferably, this device is made in two halves by anyacceptable molding or forming process. The device may be made of anyacceptable plastic material which may be cast, such as acrylics, nylons,teflons, etc. Such plastic parts may be easily cast, vacuum or injectedmolded or otherwise formed in high volumes at extremely low per unitcost, then may easily be assembled from two mating parts into the whole.If desired, the two parts may be provided with mating pegs 45 and holes46 for alignment purposes, and when so joined the half nozzles definedin each filter half and the half baffles would be in alignment, and thenform a baffle across the expansion chamber and complete openings intoand out of the expansion chamber.

Another embodiment is shown in FIG. 7 and comprises a generallycylindrical filter cartridge 50 having end walls 51 and 52. An inletopening 53 is defined in end wall 51 and outlet opening 54 is defined inend wall 52. To prevent any tendency for straight-through flow oftobacco smoke and to introduce a slight degree of turbulence, theentrances into the defined chamber 55 are made essentially radial.

The filter cartridge 50 is formed with upstanding walls 56 and 57 oneither side of outlet opening 54 as viewed in FIG. 8. A backwall orbaffie 58 joins sidewalls 56 and 57 to define a passage which isessentially radially directed out of chamber 55. Similarly, sidewalls 59and a backwall 59a (only one shown) define a similar channel leadingfrom the inlet opening 53.

It will be noted that the walls 56 and 57 are so inclined toward eachother as to provide a nozzle effect and reduce turbulence. The walls 59are similarly positioned. The backwall 59a is sufficiently spaced fromthe opening 53 so that essentially no precipitation from impingementoccurs at this point.

If desired, backwalls 58 and 59 could be made of greater length toprovide a more tortuous path, and would appear as the baffles 35 ad 36in FIG. 5.

Still another embodiment of the invention is shown in FIGS. 9 and 10wherein a generally cylindrical cartridge 60 defines an expansionchamber 61 and is so formed that the inlet port and a nozzle is definedby walls 62 and 63 which direct the incoming smoke away from thelongitudinal centerline of the cartridge 60. Similarly, the upstandingwalls 64 and 65 receive exiting smoke in a path extending away from theaxis.

In this embodiment, the filter cartridge is formed in two parts whichcomprise end wall 66 and the remainder 67 of the cartridge 60. If thenozzles were directed towards the centerline of cartridge 60, a baffie(not shown) could be displaced between the inlet and outlet opening tochange the direction of the incoming tobacco smoke and, accordingly,introduce some turbulence therein. Such baffie, if utilized, would ofcourse be sufficiently spaced from the inlet opening so as not to createan impingement precipitation effect and resulting static pressure loss.Such an arrangement is shown in FIGS. 11 and 12 and comprises .agenerally cylindrical cartridge 70 formed in two parts with an end wall71 defining an outlet opening 72. The larger cylindrical portion 73 isformed with internal walls 74 and 75 which define an inlet nozzle 76into chamber 77, and walls 78 and 79 which define an outlet channel 80to opening 72. A baffle 81 is disposed between the inlet and outletopenings to block any straight-through flow of tobacco and, also, tochange the direction of the incoming fiow of smoke and create a smalldegree of turbulence to aid in the precipitation of the tars.

FIGS. 13 and 14 illustrate another filter cartridge 82 formed in twoparts 83 and 84. The cylindrical portion 83 has a plurality oflongitudinally extending cavities 85 therein connected by passages 86 toinlet opening 87 and outlet opening 88 in end wall 84. With thisarrangement the incoming smoke will be subject to plural expansions inthe various cavities or chambers 85 to provide a multicycle expansion ordistillation process which will very effectively remove the tars in thetobacco smoke.

In all of the foregoing embodiments of the invention, for most efficientprecipitation, the volume of the precipitation or decompression chambersshould bear the ratio of to 400 numerically to the area of the inletopening when the dimensions are measured in millimeters cubed andsquared. If this ratio should be greatly exceeded, only minimalprecipitation of the tars will take place. The inner surfaces of thefilter cartridge should be maximized in area to provide the maximumsurface area for precipitation of the water vapor and accompanyingcoalescing of the tars. However, I have found that if the volume of theexpansion ismade too large, precipitation of the water vapor will notoccur.

This is believed to be due to the fact that as the volume of theexpansion chamber increases, the relation thereof to the amount of gaspulled through the inlet port becomes such that free expansion of thesmoke occurs and very little cooling of the smoke occurs. Therefore, theamount of water vapor precipitated decreases and the effectiveness ofthe filter is decreased.

On the other hand, when the smoke entering the chamber expands in aconstrained area it expands against the pressure therein or a backpressure and also experiences the internal work of separating its ownmolecules. This results in efficient cooling of the water vapor andresultant coalescing of tars.

The actual size of the outlet opening is not critical, except that itmust not reach a size which would give the chamber the effect of a largevolume. Otherwise stated, the outlet opening must have some pressuredrop thereacross to maintain some back pressure in the chamber againstwhich the incoming smoke expands.

The material of the filters is selected to preferably have a lowcoefficient of heat transfer so that heat will not be radiated from thewalls thereof and produce too much cooling of the smoke. Many smokersfind very cool smoke to be objectionable. The volume of the cartridge isselected in accordance with the inlet opening so that the cooling effectfor precipitation purposes is achieved through controlled expansionthrough the chamber and heat transfer to and through the walls of thecartridge is minimized.

The embodiment thus far disclosed are to be considered only as exemplaryof various forms and configurations in which the invention may beembodied. In particular, the nozzles disclosed thus far are forillustrative purposes only.

A cigarette filter cartridge constructed in accordance with the presentinvention introduces a moderate amount of turbulence into the tobaccosmoke entering the condensation chamber so as to produce a desiredenergy loss in the system and resulting condensation of water vapor andcoalescing of tars without introducing an objectionable pressure dropacross the system. This is achieved by providing a nozzle of decreasingcross-sectional area which protrudes into the expansion or condensationchamber. The tobacco smoke is accelerated through the nozzle ofdecreasing cross-sectional area with essentially laminar flow at highvelocity. The average volume of smoke which is aspirated by a smoker is35 milliliters during a puff of 2-second duration. The nozzle orifice isso sized that the resulting velocity through the nozzle is increased,and then suddenly decreased as the smoke enters the expansion chamber.The nozzle is preferably shaped so as to disperse the smoke upon exitingtherefrom and enhance expansion of the smoke in the chamber andresultant condensation of water vapor.

The volume of the expansion chamber is further so selected that thewater vapor will condense on the walls defining the chamber and providewetted surfaces for coalescing of the tars as the smoke loses itskinetic energy.

It is preferred to use materials of relatively poor heat conductivity,especially in the inlet and outlet openings into the chamber. Thematerials of good heat conductivity, particularly in the input nozzle,might cause condensation of tars therein resulting in full or partialobstruction and greatly increased pressure drop across the system. It isfurther preferred that the material defining the expansion chamber be ofrelatively poor heat transfer characteristics so that the condensationof water vapor and tars is due essentially to the cooling effect ofexpansion and not by the transmission of heat to the walls of thechamber.

In avoiding precipitation of any tars in the member defining the inletnozzle, it is highly advantageous to have such member extend part wayinto the cigarette receiving chamber. There is always found some littletar precipitation in this space due to turbulence. However, if thenozzle defining member extends into this space a trap is definedthereabout the tobacco or protrudes slightly and any precipitation dueto such turbulence will not be easily drawn into the inlet nozzle. Inthis embodiment the chamber is defined by the cartridge holder andspaces the cigarette from the cartridge.

The shape of the nozzles, and particularly the inlet nozzles, maycontribute to the precipitation efficiency of the unit. Where the inletis defined by a nozzlelike passage which converges toward the inletopening of the chamber, the smoke entering the chamber has betterimmediate dispersion and the pressure loss due to the nozzle is reduced.

A device with such inherently built-in opening is shown in FIGS. 15 and16 and comprises a cartridge 90 formed in two parts and joined along aline 91. An inlet passage or nozzle 92 is defined in the material of thecartridge leading to the chamber 93.

The outlet opening is also shown as an inverted nozzle 94. Howe. er, theoutlet passage may be cylindrical. The cartridge of FIG. 15 may be castin two parts and then joined together as explained in conjunction withFIG. 6.

Another and preferred form of the inlet nozzle is shown in FIG. 17 andcomprises a passage 96 of converging cross-sectional area. The contourof this nozzle along the longitudinal section line thereof is generallyellipsoid in nature. Such shape decreases the pressure loss through thenozzle and, further, by the shaping of the walls thereof reduces animmediate diverging effect on the smoke entering the chamber asindicated by the arrows A. This produces some turbulence which aids inthe precipitation of the water vapor and the coalescing of the tars.

The input nozzles may be defined in separate members which protrude intothe expansion chamber as heretofore shown in FIG. 6. FIG. 18 illustratesa nozzle defining member 98 defining a nozzle 99 generally offrustoconical configuration. Such member may be made independently andassembled with any cartridge. The divergent effect of such nozzle isexemplified by the arrows B. Similarly, in FIG. 19 a nozzle definingmember 100 may define the nozzle 101 with an ellipsoid contour. With theuse of the nozzle defining members, the

inlet opening into the chamber should be on the order previouslydescribed, that is, 0.025 inch to 0.033 inch to optimize theprecipitation of tars and not introduce an undue pressure loss. It ispreferred that the inlet diameter to the nozzle be on the order of 0.050inch and the nozzle defining members of FIGS. 18 and 19 may range from0.09 inch to 0.045 inch in length.

The invention may be embodied in filter cartridges in which thedirection of flow of the smoke after expansion thereof is caused toreverse. This provides the advantage of accelerating the particlesthrough change of direction, thus causing the forces due to suchacceleration to drive the particles toward the chamber walls.

A preferred cartridge so formed is shown in FIG. 20 as embodied in acigarette or cigar holder 102 which includes a mouthpiece portion 103.It is to be understood that the cartridge 104 may be included in afilter wrapper 14 as shown in FIG. 1 and, similarly, the filtercartridges show in FIGS. 1-16 could be made in cartridge size for acigar or cigarette holder 102, as shown in FIG. 20. The cartridge 104 isshown as comprising a chamber defining member 105 and an end piece 106carrying a nozzle 107. The chamber 108, as shown, is formed partiallycylindrical and terminating at one end in a substantially hemisphericaldome. The nozzle 107 is formed as shown in FIG. 19 to obtain maximumdispersion of the smoke as it exits therefrom into chamber 108. Thesmoke upon entering the hemispherical portion of the chamber expandsaccompanied by a decrease in temperature which precipitates moisture andtars from the smoke. The remaining gas then reverses direction and flowstowards the suction or low pressure area created in mouthpiece 103through an opening 109 defined about the nozzle 107. The opening 109 isdefined by the nozzle together with an inwardly extending flange 110.Defined in the sidewall of the cartridge are openings 111 to permit exitof the gas about the exterior of portion 105 and the holder to thepassage 112 in stem portion 103. For support and spacing purposes, aplurality of vanes 113 may be provided on the outer walls or anyconvenient portion of member 105.

The opening 109 is made of a size which will maintain a back pressure inchamber 108 to permit the desired loss of temperature upon expansion ofthe smoke without producing an objectionable static pressure drop. Thesize of the openings 1 1 1 in this form of the invention presents nocriticality.

The total volume of the chamber 108 is greater than the effective volumefor purposes of expansion. Essentially all expansion of smoke and gasestakes place between the nozzle orifice 114 and the hemispherical wall ofchamber 108, and the ratio of effective volume for expansion purposes tothe orifice area as previously set forth also remains true in thisembodiment.

It has been determined that the distance d, of the end of the nozzle 107from the backwall of chamber 108 is not critical except to the extentthat air flow resistance and, hence, pressure loss increases if thenozzle is too close. In a cartridge as shown in FIG. 20, where theradius of the hemisphere was 0.125 inch, there was no significantdifference in tar yield where the dimension d, was 0.093 inch, 0.125inch, and 0. l56 inch. However, increased air flow resistance wasdetected at the smaller dimension.

It has further been determined that when the dimension d is lengthenedthe yield of precipitated tars is increased. This is believed to be dueto the increase in the volume with increase in d which provides a plenumchamber effect and the gas pressure therein has less variation duringaspiration of smoke and a more uniform back pressure is developed in thechamber against which the incoming smoke expands. In these tests it wasnoted that all precipitated tars collected in in the hemisphericalsurfaces, indicating that precipitation of tars due to expansion of thesmoke and resulting energy loss of the system occurred in the immediateexpansion volume subsequent to entering the chamber.

The length of protrusion of the nozzle 107 into chamber 108 must not beso shortened that it provides a short circuit path from the nozzle tothe opening 109.

The cartridge 104 may be further modified to eliminate the flange 110and, therefore, the opening 109. In such modification, the openings 111are then properly sized to maintain the necessary back pressure inchamber 108.

This arrangement, providing the reverse flow, offers the advantage thatthere is no possibility of a straight-through flow of gases withoutexpansion thereof and, further, a greater amount of surface area forprecipitation in coalescing of tars is provided. In tests it has beenfound, however, that by far the greatest amount of tars will precipitateimmediately upon expansion thereof on the walls defining thehemispherical portron.

The nozzle defining member extends without the cartridge to define ashort passage 115 defined by walls 115a. This prevents any tarsprecipitated in the areas 115b from entering nozzle 107. Where thefilter is carried in a holder, the spacers for the cigarette may bedefined in the holder.

Another cartridge operating on this principle is shown in FIGS. 21 and22 and comprises a housing 116 defining a cylindrical chamber 117 with awall 118 therein defining with the housing a passage 119. The wall 118has an aperture 120 therein which together with nozzle 12 defines anoutlet opening. The nozzle 121 is shown as a cylindrical passageway forsimplicity of illustration. However, it will be understood that it willpreferably take the same form as the nozzle shown in FIGS. 19 and 20.Upon entrance of the smoke into the chamber 117, it expands primarilybetween the end of nozzle 121 and the walls of the chamber therebehind.Thereafter, the gas will flow towards the opening 120 in passage 112 instem 103. The nozzle defining member 121 may have an externallyprotruding extension 122 for the purposes previously described. Suchextension may itself be tapered to enhance essentially laminar flow inthe nozzle.

Still another embodiment of the invention utilizing the same reverseflow principle is illustrated in FIGS. 23 and 24. In this embodiment, ahousing member 124 defines an expansion chamber 125 and an outletpassage 126 thereabout separated by the wall 127. Wall 127 together withnozzle 128 defines an outlet opening 129 about the nozzle. Vanes orbaffles 130 and 131, straight or curved, are provided to define gasdirecting passages 132 and 133, respectively, and present more surfacefor condensation. The nozzle 128 is shown as defining a cylindricalpassage for simplicity of illustration. However, it is to be understoodthat the preferred nozzle is shaped as shown in FlGS. 18 or 19 and 20.Upon entrance of the smoke through nozzle 128 into chamber 125, itexpands upon leaving the nozzle with the resulting decrease in energyand loss of temperature which results in precipitation of moisture andcoalescing of the tars. The gas then proceeds between baffles or vanes130 and 131 and reverses flow through passages 132 and 133 towardsopening 129. Hence, it is drawn through passages 126 into the passage112 in stem 103. The nozzle defining member 128 may be provided with anexternal extension 134 for reasons previously described.

It will be apparent that the filter cartridges shown in FIGS. 2024 mayreadily be disposed of and replaced in the holder. Tests have shown thatsuch filter cartridges are effective for use with five or morecigarettes of the so-called king size.

Tests have further shown that cartridges of the type disclosed operatingon the expansion and precipitation principle are 30 to 50 percent moreeffective in the yield of tars and other matters from tobacco smoke thanthe commercially available filters of the type described in U.S. Pat.No. 2,954,779, which operates on the impingement principle, and wherethe pressure drop through the filter is the same. It has been determinedthat devices embodying the present invention may be sized to produce anapproximately 25 percent lower pressure drop than the commerciallyavailable filters of the type shown in the aforementioned patent andstill produce the same yield as such commercially available device.

Comparative tests were made on a Kent king size cigarette with itsincluded filter removed between a cartridge as shown in FIG. 20 and oneknown as Tar-Gard constructed in accordance with U.S. Pat. No.2,954,779.

These tests were made under the following conditions:

a. Each puff was 35 milliliters.

b. Each puff has a duration of 2 seconds.

c. The pufis were produced by sinusoidal pressure changes.

d. One puff per minute.

e. Total of eight puffs.

The tests revealed that the filter, as shown in FIG. 20, removed, on theaverage, at least 50 percent more tar than the one constructed inaccordance with U.S. Pat. No. 2,954,779.

It may thus be seen that the objects of the invention set forth above,as well as those made apparent from the foregoing description, areefficiently attained. While a preferred embodiment of the invention hasbeen set forth for purposes of disclosure, other embodiments of theinvention as well as modifications to the disclosed embodiments mayoccur to those skilled in the art which do not depart from the spiritand scope of the invention. It is therefore intended in the appendedclaims to cover all embodiments'of the invention as well asmodifications to the disclosed embodiments of the invention which do notdepart from the spirit and scope of the invention.

We claim:

1. A device for removing tars from tobacco smoke passing therethroughcomprising means defining a chamber having internal walls, meansdefining an inlet nozzle extending into said chamber, said nozzle havingan opening diameter of from 0.025 inch to 0.033 inch, an outlet openingdefined in said chamber, said nozzle opening being spaced from saidwalls and said chamber having a volume sufficient to permit substantialexpansion of smoke therein entering from said nozzle prior to the smokecontacting said walls, said nozzle being constructed and arranged toproduce dispersion of smoke entering therethrough to said chamber, saidoutlet opening having an area at least twice as large as the area ofsaid nozzle opening and being sized in relation to the volume of saidchamber to produce a pressure drop thereacross as smoke is drawn throughsaid device so that expansion of the smoke in said chamber produces adrop in temperature of the smoke in said chamber causing precipitationof tars in the smoke on said walls and said outlet opening beingpositioned intermediate the ends of the passage defined by said nozzle.

2. A device for removing tars from tobacco smoke passing therethroughcomprising means defining a hollow chamber having internal walls, meansdefining an inlet nozzle extending into said chamber, said nozzle beingso shaped as to cause dispersion of smoke in said chamber as the smokeenters the chamber through said nozzle, said nozzle having an openingdiameter of from 0.025 inch to 0.033 inch, an outlet opening defined insaid chamber, said chamber having a volume sufficient to permitexpansion of smoke therein entering from said nozzle so as toprecipitate tars from the smoke, said nozzle opening being spaced fromsaid walls a sufficient distance so that substantial expansion of smokeentering said chamber occurs prior to the smoke contacting said walls,said outlet opening having an area at least twice as large as the areaof said nozzle opening, said outlet opening being defined in saidchamber upstream the opening of said nozzle in said chamber so thatsmoke entering said chamber reverses direction between the inlet andoutlet openings, said outlet opening being sized to produce a pressuredrop thereacross as smoke is drawn through said device so that expansionof smoke in said chamber produces a drop in temperature of the smoke insaid chamber causing precipitation of tars in the smoke on said walls.

3. The device of claim 2 wherein the longitudinal cross-sectionalcontour of said nozzle defines a portion of an ellipsoid.

4. The device of claim 2 wherein the longitudinal cross-sectionalcontour of said nozzle is defined by lines converging from the inlet tooutlet of approximately 30.

5. The device of claim 2 wherein the outlet opening of said chamber isdefined in said chamber between the inlet and outlet of said nozzle.

6. The device of claim 2 wherein the chamber wall opposite said nozzleis longitudinally concave in the direction facing the outlet portion ofsaid nozzle.

7. The device of claim 2 wherein the means defining said nozzle is of anonmetallic material.

8. A tobacco smoke filter comprising wall means defining a chamber forexpansion of smoke therein, a nozzle extending into said chamber anddefining an inlet passage therein, the opening in said nozzle in saidchamber being spaced from said wall means in said chamber for definingwith said wall means a volume sufficient to permit substantial expansionof smoke therein entering from said nozzle prior to the smoke contacting said wall means, an outlet opening from said chamber, said outletopening being positioned intermediate the ends of the passage defined bysaid nozzle, said outlet opening being sized in relation to the volumeof said chamber to produce a pressure drop thereacross as smoke is drawnthrough said device so that expansion of the smoke in said chamberproduces a drop in temperature of the smoke in said chamber causingprecipitation of the tars in the smoke on said wall means.

9. The filter of claim 8 wherein said outlet opening is coaxial withsaid nozzle.

10. The filter of claim 8 wherein said outlet opening has across-sectional area selected to create back pressure within saidchamber and prevent unlimited expansion of tobacco smoke entering saidchamber through said nozzle.

11. The filter of claim 8 wherein the wall defining said chamberopposite said nozzle is substantially hemispherical, said wall extendingtransversely across the outlet portion of said nozzle.

12. The filter of claim 8 further including wall means defining apassage with the outer walls of said chamber, said outlet opening ofsaid chamber communicating with said passage.

13. The filter device of claim 8 wherein said nozzle has a length of0.045 inch to 0.10 inch and a decreasing cross-sectional area along thelength thereof toward the outlet opening.

14. The device of claim 13 wherein said nozzle has an opening into saidchamber of 0.025 inch to 0.033 inch diameter.

15. The device of claim 13 wherein the diameter of the smoke intake endof said nozzle is approximately twice the diameter of the smoke outletend.

16. The device of claim 13 wherein said nozzle defining means extendsoutwardly of said chamber defining means towards a smoke producingarticle.

17. A device for removing tars from tobacco smoke passing therethroughcomprising means defining a hollow chamber having internal walls, meansdefining an inlet nozzle extending into said chamber, said nozzle beingso shaped as to cause dispersion of smoke in said chamber as the smokeenters the chaml: r through said nozzle, said nozzle having an openingdiameter of from 0.025 in. to 0.033 in., an outlet opening defined insaid chamber, said chamber having a volume sufficient to permitexpansion of smoke therein entering from said nozzle so as toprecipitate tars from the smoke, said nozzle opening being spaced fromsaid walls a sufficient distance so that substantial expansion of smokeentering said chamber occurs prior to the smoke contacting said walls,the volume of said chamber for expansion of smoke therein expressed incubic millimeters being to 400 times greater than the area of saidnozzle opening expressed in square millimeters, said outlet openinghaving an area at least twice as large as the area of said nozzleopening, said outlet opening being defined in said chamber upstream theopening of said nozzle in said chamber so that smoke entering saidchamber reverses direction between the inlet and outlet openings, saidoutlet opening being sized to produce a pressure drop thereacross assmoke is drawn through said device so that expansion of smoke in saidchamber produces a drop in temperature of the smoke in said chambercausing precipitation of tars in the smoke on said walls.

1 The device of claim 17 wherein the longitudinal crosssectional contourof said nozzle defines a portion of an ellipsoid.

19. The device of claim 17 wherein the longitudinal crosssectionalcontour of said nozzle is defined by lines converging from the inlet ofthe nozzle to the outlet of the nozzle by approximately 30.

20. The device of claim 17 wherein the outlet opening of said chamber isdefined in said chamber between the inlet and outlet of said nozzle.

21. The device of claim 17 wherein the chamber wall opposite said nozzleis longitudinally concave in the direction facing the outlet portion ofsaid nozzle.

22. The device of claim 17 wherein the means defining said nozzle is ofa nonmetallic material.

23. A tobacco smoke filter comprising wall means defining a chamber forexpansion of smoke therein, a nozzle extending into said chamber anddefining an inlet passage therein, an opening on said nozzle in saidchamber being spaced from said wall means in said chamber for definingwith said wall means an volume sufficient to permit substantialexpansion of smoke therein entering from said nozzle prior to the smokecontacting said wall means, the volume of said chamber for expansion ofsmoke therein expressed in cubic millimeters being' lOO to 400 timesgreater than the area of said nozzle opening expressed in squaremillimeters, an outlet opening from said chamber, said outlet openingbeing positioned intermediate the ends of the passage defined by saidnozzle, said outlet opening having a cross-sectional area selected inrelation to the volume of said chamber to produce a pressure dropthereacross as smoke is drawn through said device so that expansion ofthe smoke in said chamber produces a drop in temperature of the smoke insaid chamber causing precipitation of the tars in the smoke on said wallmeans.

24. The filter of claim 23 wherein said outlet opening is coaxial withsaid nozzle.

25. The filter of claim 23 wherein said outlet opening has across-sectional area sufficient to create back pressure within saidchamber and prevent unlimited expansion of tobacco smoke entering saidchamber through said nozzle.

26. The filter of claim 23 wherein the wall defining said chamberopposite said nozzle is substantially hemispherical, said wall extendingtransversely across the outlet portion of said nozzle.

27. The filter of claim 23 further including wall means defining apassage with the outer walls of said chamber, said outlet opening ofsaid chamber communicating with said passage.

g g UNITED STATES PATENT OFFICE 4 CERTIFICATE OF CORRECTION Patent No;3,601,133 D t d August 2 4, 1971 Inventot(e) William F. Van Eck WarrenR. Jewett It is certified that error appears in the above-identifiedpatent end that said Letters Patent are hereby corrected as shown below:

I- w Column 2, line 11, after "water" insert vapor Line 16, "droplet"should be droplets Line 75, "ad" should be and Column 3, line 61, "FIG.2" should be FIG. 22 Column 6, line 67, "embodiment" should beembodiments Column 8, line 71, delete "in" (secondoccurrence). Column 9,line 25, "nozzle 12" should be nozzle 121 Column 12, line 33, "an"should be a Signed and sealed this fi th day of March 1972.

(SEAL) Attest: I

EDWARD M.FLETCHER,JR ROBERT GOTTSCHALK Attesting Officer CommissionerofPatents

2. A device for removing tars from tobacco smoke passing therethroughcomprising means defining a hollow chamber having internal walls, meansdefining an inlet nozzle extending into said chamber, said nozzle beingso shaped as to cause dispersion of smoke in said chamber as the smokeenters the chamber through said nozzle, said nozzle having an openingdiameter of from 0.025 inch to 0.033 inch, an outlet opening defined insaid chamber, said chamber having a volume sufficient to permitexpansion of smoke therein entering from said nozzle so as toprecipitate tars from the smoke, said nozzle opening being spaced fromsaid walls a sufficient distance so that substantial expansion of smokeentering said chamber occurs prior to the smoke contacting said walls,said outlet opening having an area at least twice as large as the areaof said nozzle opening, said outlet opening being defined in saidchamber upstream the opening of said nozzle in said chamber so thatsmoke entering said chamber reverses direction between the inlet andoutlet openings, said outlet opening being sized to produce a pressuredrop thereacross as smoke is drawn through said device so that expansionof smoke in said chamber produces a drop in temperature of the smoke insaid chamber causing precipitation of tars in the smoke on said walls.3. The device of claim 2 wherein the longitudinal cross-sectionalcontour of said nozzle defines a portion of an ellipsoid.
 4. The deviceof claim 2 wherein the longitudinal cross-sectional contour of saidnozzle is defined by lines converging from the inlet to outlet ofapproximately 30*.
 5. The device of claim 2 wherein the outlet openingof said chamber is defined in said chamber between the inlet and outletof said nozzle.
 6. The device of claim 2 wherein the chamber wallopposite said nozzle is longitudinally concave in the direction facingthe outlet portion of said nozzle.
 7. The device of claim 2 wherein themeans defining said nozzle is of a nonmetallic material.
 8. A tobaccosmoke filter comprising wall means defining a chamber for expansion ofsmoke therein, a nozzle extending into said chamber and defining aninlet passage therein, the opening in said nozzle in said chamber beingspaced from said wall means in said chamber for defining with said wallmeans a volume sufficient to permit substantial expansion of smoketherein entering from said nozzle prior to the smoke contacting saidwall means, an outlet opening from said chamber, said outlet openingbeing positioned intermediate the ends of the passage defined by saidnozzle, said outlet opening being sized in relation to the volume ofsaid chamBer to produce a pressure drop thereacross as smoke is drawnthrough said device so that expansion of the smoke in said chamberproduces a drop in temperature of the smoke in said chamber causingprecipitation of the tars in the smoke on said wall means.
 9. The filterof claim 8 wherein said outlet opening is coaxial with said nozzle. 10.The filter of claim 8 wherein said outlet opening has a cross-sectionalarea selected to create back pressure within said chamber and preventunlimited expansion of tobacco smoke entering said chamber through saidnozzle.
 11. The filter of claim 8 wherein the wall defining said chamberopposite said nozzle is substantially hemispherical, said wall extendingtransversely across the outlet portion of said nozzle.
 12. The filter ofclaim 8 further including wall means defining a passage with the outerwalls of said chamber, said outlet opening of said chamber communicatingwith said passage.
 13. The filter device of claim 8 wherein said nozzlehas a length of 0.045 inch to 0.10 inch and a decreasing cross-sectionalarea along the length thereof toward the outlet opening.
 14. The deviceof claim 13 wherein said nozzle has an opening into said chamber of0.025 inch to 0.033 inch diameter.
 15. The device of claim 13 whereinthe diameter of the smoke intake end of said nozzle is approximatelytwice the diameter of the smoke outlet end.
 16. The device of claim 13wherein said nozzle defining means extends outwardly of said chamberdefining means towards a smoke producing article.
 17. A device forremoving tars from tobacco smoke passing therethrough comprising meansdefining a hollow chamber having internal walls, means defining an inletnozzle extending into said chamber, said nozzle being so shaped as tocause dispersion of smoke in said chamber as the smoke enters thechamber through said nozzle, said nozzle having an opening diameter offrom 0.025 in. to 0.033 in., an outlet opening defined in said chamber,said chamber having a volume sufficient to permit expansion of smoketherein entering from said nozzle so as to precipitate tars from thesmoke, said nozzle opening being spaced from said walls a sufficientdistance so that substantial expansion of smoke entering said chamberoccurs prior to the smoke contacting said walls, the volume of saidchamber for expansion of smoke therein expressed in cubic millimetersbeing 100 to 400 times greater than the area of said nozzle openingexpressed in square millimeters, said outlet opening having an area atleast twice as large as the area of said nozzle opening, said outletopening being defined in said chamber upstream the opening of saidnozzle in said chamber so that smoke entering said chamber reversesdirection between the inlet and outlet openings, said outlet openingbeing sized to produce a pressure drop thereacross as smoke is drawnthrough said device so that expansion of smoke in said chamber producesa drop in temperature of the smoke in said chamber causing precipitationof tars in the smoke on said walls.
 18. The device of claim 17 whereinthe longitudinal cross-sectional contour of said nozzle defines aportion of an ellipsoid.
 19. The device of claim 17 wherein thelongitudinal cross-sectional contour of said nozzle is defined by linesconverging from the inlet of the nozzle to the outlet of the nozzle byapproximately 30*.
 20. The device of claim 17 wherein the outlet openingof said chamber is defined in said chamber between the inlet and outletof said nozzle.
 21. The device of claim 17 wherein the chamber wallopposite said nozzle is longitudinally concave in the direction facingthe outlet portion of said nozzle.
 22. The device of claim 17 whereinthe means defining said nozzle is of a nonmetallic material.
 23. Atobacco smoke filter comprising wall means defining a chamber forexpansion of smoke therein, a nozzle extending into said chamber anddefining an inlet passage therein, an opening on said nozzle in saidchamber being spaced from said wall means in said chamber for definingwith said wall means an volume sufficient to permit substantialexpansion of smoke therein entering from said nozzle prior to the smokecontacting said wall means, the volume of said chamber for expansion ofsmoke therein expressed in cubic millimeters being 100 to 400 timesgreater than the area of said nozzle opening expressed in squaremillimeters, an outlet opening from said chamber, said outlet openingbeing positioned intermediate the ends of the passage defined by saidnozzle, said outlet opening having a cross-sectional area selected inrelation to the volume of said chamber to produce a pressure dropthereacross as smoke is drawn through said device so that expansion ofthe smoke in said chamber produces a drop in temperature of the smoke insaid chamber causing precipitation of the tars in the smoke on said wallmeans.
 24. The filter of claim 23 wherein said outlet opening is coaxialwith said nozzle.
 25. The filter of claim 23 wherein said outlet openinghas a cross-sectional area sufficient to create back pressure withinsaid chamber and prevent unlimited expansion of tobacco smoke enteringsaid chamber through said nozzle.
 26. The filter of claim 23 wherein thewall defining said chamber opposite said nozzle is substantiallyhemispherical, said wall extending transversely across the outletportion of said nozzle.
 27. The filter of claim 23 further includingwall means defining a passage with the outer walls of said chamber, saidoutlet opening of said chamber communicating with said passage.